Return only string message from Spring MVC 3 Controller
JavaSpringSpring MvcJava Problem Overview
Can any one tell me how I can return string message from controller?
If i just return a string from a controller method then spring mvc treating it as a jsp view name.
Java Solutions
Solution 1 - Java
Annotate your method in controller with @ResponseBody
:
@RequestMapping(value="/controller", method=GET)
@ResponseBody
public String foo() {
return "Response!";
}
From: 15.3.2.6 Mapping the response body with the @ResponseBody
annotation:
> The @ResponseBody
annotation [...] can be put on a method and indicates that the return type should be written straight to the HTTP response body (and not placed in a Model, or interpreted as a view name).
Solution 2 - Java
With Spring 4, if your Controller is annotated with @RestController
instead of @Controller
, you don't need the @ResponseBody
annotation.
The code would be
@RestController
public class FooController {
@RequestMapping(value="/controller", method=GET)
public String foo() {
return "Response!";
}
}
You can find the Javadoc for @RestController
here
Solution 3 - Java
Although, @Tomasz is absolutely right there is another way:
@RequestMapping(value="/controller", method=GET)
public void foo(HttpServletResponse res) {
try {
PrintWriter out = res.getWriter();
out.println("Hello, world!");
out.close();
} catch (IOException ex) {
...
}
}
but the first method is preferable. You can use this method if you want to return response with custom content type or return binary type (file, etc...);
Solution 4 - Java
This is just a note for those who might find this question later, but you don't have to pull in the response to change the content type. Here's an example below to do just that:
@RequestMapping(method = RequestMethod.GET, value="/controller")
public ResponseEntity<byte[]> displayUploadedFile()
{
HttpHeaders headers = new HttpHeaders();
String disposition = INLINE;
String fileName = "";
headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
//Load your attachment here
if (Arrays.equals(Constants.HEADER_BYTES_PDF, contentBytes)) {
headers.setContentType(MediaType.valueOf("application/pdf"));
fileName += ".pdf";
}
if (Arrays.equals(Constants.HEADER_BYTES_TIFF_BIG_ENDIAN, contentBytes)
|| Arrays.equals(Constantsr.HEADER_BYTES_TIFF_LITTLE_ENDIAN, contentBytes)) {
headers.setContentType(MediaType.valueOf("image/tiff"));
fileName += ".tif";
}
if (Arrays.equals(Constants.HEADER_BYTES_JPEG, contentBytes)) {
headers.setContentType(MediaType.IMAGE_JPEG);
fileName += ".jpg";
}
//Handle other types if necessary
headers.add("Content-Disposition", , disposition + ";filename=" + fileName);
return new ResponseEntity<byte[]>(uploadedBytes, headers, HttpStatus.OK);
}
Solution 5 - Java
What about:
PrintWriter out = response.getWriter();
out.println("THE_STRING_TO_SEND_AS_RESPONSE");
return null;
This woks for me.
Solution 6 - Java
For outputing String
as text/plain
use:
@RequestMapping(value="/foo", method=RequestMethod.GET, produces="text/plain")
@ResponseBody
public String foo() {
return "bar";
}
Solution 7 - Java
@Controller
public class HelloController {
@RequestMapping(value = "/", method = RequestMethod.GET)
ResponseEntity<String> sayHello() {
return ResponseEntity.ok("Hello");
}
}
Solution 8 - Java
Simplest solution:
Just add quotes, I really don't know why it's not auto-implemented by Spring boot when response type defined as application/json, but it works great.
@PostMapping("/create")
public String foo()
{
String result = "something"
return "\"" + result + "\"";
}
Solution 9 - Java
There are two possible solution
-
Use
@Controller
and@ResponseBody
, to combine HTML page and the string message for different functions@Controller @RequestMapping({ "/user/registration"}) public class RegistrationController { @GetMapping public String showRegistrationForm(Model model) { model.addAttribute("user", new UserDto()); return "registration"; //Returns the registration.html } @PostMapping @ResponseBody public String registerUserAccount(@Valid final UserDto accountDto, final HttpServletRequest request) { LOGGER.debug("Registering user account with information: {}", accountDto); return "Successfully registered" // Returns the string }
-
Use
@RestController
to return String message. In this case, you cannot have functions which returns HTML page.@RestController @RequestMapping({ "/user/registration"}) public class RegistrationController { @PostMapping public String registerUserAccount(@Valid @RequestBody final UserDto accountDto, final HttpServletRequest request) { LOGGER.debug("Registering user account with information: {}", accountDto); return "Successfully registered" // Returns the string }
Solution 10 - Java
@ResponseBody
@RequestMapping(value="/get-text", produces="text/plain")
public String myMethod() {
return "Response!";
}
- You see that
@ResponseBody
?
> It's telling that the method returns some text and not to interpret > it as a view etc.
- You see that
produces="text/plain"
?
> It's just a good practice as it tells what will be returned from the > method :)